1. Field of the Invention
The present invention relates to a printing technique suitable for forming high-precision patterns for image forming device parts, printed circuit boards, etc., and particularly relates to an offset printing method and offset printing apparatus suitable for plate-shaped work such as large-area glass plates, epoxy plates, and so forth.
2. Description of the Related Art
Conventionally, the screen printing method has been known as a method used for forming patterns by printing on plate-shaped work such as glass plates, epoxy plates, and so forth, for electronic industry purposes. Also, a supporting structure for the screen thereof has been proposed as the method disclosed in Japanese Patent Laid-open Publication No. 1-182047.
However, in recent years, high-precision patterns for color filter substrates and circuit boards for image forming devices have come to require resolution of 50 xcexcm and smaller, and thus the offset printing method has come into use. Regarding the type of offset printing method, the work is a flat plate, so flatbed proof press types are normally used. Also, recently, liquid crystal displays from 2 to 20 inches in size, and wall-type TVs 30 to 60 inches in size have come to greatly vary image forming apparatuses. Accordingly, large-size offset printers capable of dealing with large work sizes have come into need. Incidentally, recent patent publications (i.e., Japanese Patent Laid-open Publication No. 5-169622, Japanese Patent Laid-open Publication No. 6-171062, and Japanese Patent Laid-open Publication No. 7-125179) also disclose an offset printing method which differs in form from those used so far. The publications describe using an ink sheet (blanket) supported in the form of a flat plate.
However, with conventional offset printers which contain flatbed proof presses, the area of the plate surface table 701 and work surface table 702, shown in FIG. 20, must be increased in order to deal with large work sizes. In addition, the sideways width and diameter of the blanket drum 703 for mounting the blanket 704 also have to be increased. Further, the nip width 707 formed by the blanket 704 coming in contact with the plate 705 or the work 706 during printing must necessarily increase along with the increase in the diameter of the blanket drum 703, even if the printing pressure (amount of depressing) conditions are the same. Accordingly, the amount of deformation of the surface rubber on the blanket 704 increases, causing the problem of deterioration in printing pattern form. Further, the apparent approach angle xe2x80x9cxcex1xe2x80x9d and the departing angle xe2x80x9cxcex2xe2x80x9d formed by the blanket 704 coming in contact with the plate 705 or the work 706 during printing decreases as the diameter of the blanket drum 703 increases, and thus, there is the problem in that the reception and transfer of ink becomes unstable.
With the offset printing method disclosed in Japanese Patent Laid-open Publication No. 5-169622, Japanese Patent Laid-open Publication No. 6-171062, and Japanese Patent Laid-open Publication No. 7-125179, wherein an ink sheet (blanket) supported in a flat plate form is used, it is thought that the above problem of deterioration in printing pattern form can be avoided. However, the ink sheet (blanket) is fixed to a frame, so the approach angle xe2x80x9caxe2x80x9d and the departing angle xe2x80x9cbxe2x80x9d cannot be set very large, and further it becomes impossible to maintain both the approach angle xe2x80x9caxe2x80x9d and the departing angle xe2x80x9cbxe2x80x9d at appropriate angles from the point of beginning printing to the end thereof, and accordingly the problem of unstable ink reception and transfer still remains. In addition to this, the edges of the ink sheet (blanket) perpendicular to the printing direction are also fixed to the frame, so irregularities in tension are generated between the center portion and the perimeter portions at the time of printing, and in the event that the pressuring conditions at the time of ink reception and at the time of transfer differ, this causes a problem of deterioration in printing position precision.
The present invention has been made in light of the above, and it is an object thereof to provide an offset printing method and offset printing apparatus capable of securing excellent pattern form, ink receiving/transferring properties, and positional precision, for large plate-shaped work, as well.
That is, according to a first aspect of the present invention, an offset printing method comprises the steps of: a process for suspending a sheet-shaped or belt-shaped blanket by supporting both ends thereof at the leading and trailing ends thereof in the printing direction; and a process for performing ink reception from a plate to the blanket and also transferring ink from the blanket to a work, by pressing the blanket by a pressuring jig from an upwards direction down onto a plate or work situated below and sweeping in the printing direction.
Also, according to a second aspect of the present invention, an offset printing method comprises the steps of: a process for suspending a sheet-shaped or belt-shaped blanket by supporting both ends thereof at the leading and trailing ends thereof in the printing direction; a process for performing ink reception from a plate to the blanket and also transferring ink from the blanket to a work, by pressing the blanket by a pressuring jig from an upwards direction down onto a plate or work situated below and sweeping in the printing direction; and a process for correcting the amount of error in printing dimensions which occur at the time of the ink reception or the ink transferring, by moving the printing surface table by an appropriate value at the time of the ink reception or the ink transferring.
Also, according to a third aspect of the present invention, an offset printing method comprises the steps of: a process for suspending a sheet-shaped or belt-shaped blanket by supporting both ends thereof at the leading and trailing ends thereof in the printing direction; a process for performing ink reception from a plate to the blanket and also transferring ink from the blanket to a work, by pressing the blanket by a pressuring jig from an upwards direction down onto a plate or work situated below and sweeping in the printing direction; and a process for sequentially feeding an area used for the ink reception and transfer every certain arbitrary number of printing times.
Also, according to a fourth aspect of the present invention, an offset printing method comprises the steps of: a process for suspending a sheet-shaped or belt-shaped blanket by supporting both ends thereof at the leading and trailing ends thereof in the printing direction; a process for performing ink reception from a plate to the blanket and also transferring ink from the blanket to a work, by pressing the blanket by a pressuring jig from an upwards direction down onto a plate or work situated below and sweeping in the printing direction; and a process for controlling each of the tensions of the blanket divided by the pressuring jig, either at one end of the blanket or at both ends thereof.
Also, according to a fifth aspect of the present invention, an offset printing apparatus has a blanket for receiving ink from a plate and transferring the ink to a work, and supporting members for the blanket; wherein the blanket is sheet-shaped or belt-shaped, and the blanket supporting members are two opposing shafts extending vertically with respect to the printing direction and the leading and trailing ends of the printing direction, for suspending the blanket by supporting both ends thereof; and wherein the offset printing apparatus further comprises a pressuring jig for pressing the blanket from an upwards direction down onto a plate or work situated below and sweeping in the printing direction.
Also, according to a sixth aspect of the present invention, an offset printing apparatus has a blanket for receiving ink from a plate and transferring the ink to a work, and supporting members for the blanket; wherein the blanket is sheet-shaped or belt-shaped, and the blanket supporting members are two opposing shafts extending vertically with respect to the printing direction and the leading and trailing ends of the printing direction, for suspending the blanket by supporting both ends thereof; and wherein the offset printing apparatus further comprises:
a pressuring jig for pressing the blanket from an upwards direction down onto a plate or work situated below, band sweeping in the printing direction; and
means for moving the printing surface table.
Also, according to a seventh aspect of the present invention, an offset printing apparatus has a blanket for receiving ink from a plate and transferring the ink to a work, and supporting members for the blanket; wherein the blanket is sheet-shaped or belt-shaped, and the blanket supporting members are two opposing shafts extending vertically with respect to the printing direction and the leading and trailing ends of the printing direction, for suspending the blanket by supporting both ends thereof; and wherein the offset printing apparatus further comprises:
a pressuring jig for pressing the blanket from an upwards direction down onto a plate or work situated below, and sweeping in the printing direction; and
a mechanism for sequentially feeding the area of the blanket used for the ink reception and transfer every certain arbitrary number of printing times.
Also, according to an eighth aspect of the present invention, an offset printing apparatus has a blanket for receiving ink from a plate and transferring the ink to a work, and supporting members for the blanket; wherein the blanket is sheet-shaped or belt-shaped, and the blanket supporting members are two opposing shafts extending vertically with respect to the printing direction and the leading and trailing ends of the printing direction, for suspending the blanket by supporting both ends thereof; and wherein the offset printing apparatus further comprises:
a pressuring jig for pressing the blanket from an upwards direction down onto a plate or work situated below, and sweeping in the printing direction; and
means for adjusting the tension of the blanket.
Also, according to a ninth aspect of the present invention, an offset printing apparatus has a blanket for receiving ink from a plate and transferring the ink to a work, and supporting members for the blanket; wherein the blanket is sheet-shaped or belt-shaped, and the blanket supporting members are two opposing shafts extending vertically with respect to the printing direction and the leading and trailing ends of the printing direction, for suspending the blanket by supporting both ends thereof; and wherein the offset printing apparatus further comprises a pressuring jig for pressing the blanket from an upwards direction down onto a plate or work situated below on a printing surface table, and sweeping in the printing direction; and wherein the supporting members are supporting structures movable in the printing direction.
Also, according the tenth aspect of the present invention, an offset printing apparatus has a blanket for receiving ink from a plate and transferring the ink to a work, and supporting members for the blanket; wherein the blanket is sheet-shaped or belt-shaped, and the blanket supporting members are two opposing shafts extending vertically with respect to the printing direction and the leading and trailing ends of the printing direction, for suspending the blanket by supporting both ends thereof; and wherein the offset printing apparatus further comprises a pressuring jig for pressing the blanket from an upwards direction down onto a plate or work situated below, and sweeping in the printing direction; and wherein the pressuring jig comprises a roller for pressing the blanket.